1. Field of Invention
This invention concerns methods and systems for cleaning ink jet print heads.
2. Description of Related Art
Some ink jet printer print heads which use water based inks, such as, for example, acoustic ink jet print heads, are difficult to clean. Ink jet printers that use such difficult-to-clean print heads employ cleaning systems which become soiled over time. These soiled cleaning systems typically have to be replaced at regular intervals. Ink jet printers that use such difficult-to-clean print heads also typically use complex seal mechanisms at the print head-cleaning system interface to prevent cleaning fluid from spilling or otherwise leaking at the interface.
Some cleaning systems use rotating cleaning rollers that dip into cleaning fluid contained in a cleaning chamber. In operation, a squeegee roller bears against the cleaning roller and squeezes out excess cleaning fluid. Then, a rotating cleaning roller bears against the print head to apply cleaning fluid to the soiled print head. The applied cleaning fluid dissolves and washes away dried ink, including dried ink plugs, paper dust and other print head contaminants from the print head orifices into the cleaning fluid in the cleaning chamber, where the dried ink and other contaminants are dissolved into the cleaning fluid contained in the cleaning chamber.
Problems with ink jet print head cleaning systems include buildup of ink and/or other contaminants in the cleaning fluid with each cleaning cycle, and evaporation of water and other non-volatile liquids from the cleaning solutions during periods of non-use. These problems sharply reduce the useful life of cleaning fluids by increasing the concentration levels of ink in the cleaning fluid.
That is, the concentration ratio of ink to cleaning fluid in the cleaning fluid contained in the cleaning chamber increases as the cleaning fluid is used to clean the print head. As a result, the cleaning fluid becomes less efficient at cleaning the print heads. After a certain number of cleaning cycles, the cleaning fluid resident in the cleaning chamber becomes too contaminated to effectively clean print heads.
This invention provides methods and systems that maintain the concentration of ink in the cleaning fluid throughout the life of the printer at levels where the effectiveness of the cleaning fluid in removing contaminants is not substantially impaired.
This invention separately provides systems and methods that compensate for and/or reduce the evaporation of volatile chemical compounds from the cleaning fluid.
This invention separately provides systems and methods that reduce the build-up of ink and/or other contaminants in the cleaning fluid.
This invention separately provides cleaning systems that reduce the need to use complicated seal mechanisms to contain the cleaning fluid in the cleaning system.
In various exemplary embodiments, one or more of these features are provided by pumping cleaning fluid into the print head cleaning chamber only when one or more of the print heads need to be cleaned. After the print head cleaning operation is completed, the cleaning fluid left in the cleaning chamber is removed from the cleaning chamber and sent to holding tanks, which are closed containers where the cleaning fluids are held to prevent evaporation of volatile materials in the cleaning fluid.
At various intervals, a known amount of contaminated cleaning fluid is removed from one or more of the holding tanks to a leach bed. The leach bed has a capacity to hold waste cleaning fluid bled to it from the holding tanks and is able to evaporate the waste cleaning fluid effectively over the life of the printer. A measured amount of fresh, i.e., uncontaminated, make-up cleaning fluid is then added into the one or more holding tanks from a corresponding cleaning fluid container. This results in maintaining the ink/cleaning fluid concentration in the holding tanks within ranges which result in effective long term cleaning of the print heads, e.g., for the useful life of the printer. This can also compensate for any volatile compounds lost from the usable cleaning fluid due to evaporation.
These and other features and advantages of this invention are described in, or are apparent from, the following detailed description of various exemplary embodiments of the systems and methods according to this invention.